If each mile costs $3, 2 miles would cost $11.
$6 plus the flat fee of $5.
How much would 8 miles cost?

2 miles : $11
8 miles: $29

If we let a variable represent the miles traveled, we can create an expression to represent the cost for her transportation.

Since each mile costs $3, this can be represented as $3(x).
Because she had to also pay a flat fee, this can be represented as a constant, $5.

$3(x) + $5

$3(x) + $5 = $23
How many miles did she travel?